The Diversity of Prokaryotes and Viruses

BIO 101

Life Science

Dr. D. L. Daley

Bacterial Classification

Bacteria or Eubacteria - most common prokaryotic cells

Cell walls contain peptidoglycans

Archaea or Archebacteria - tend to live in extreme environments

Cell walls do not contain peptidoglycans

Metabolic Diversity

Autotrophs - Carbon from CO₂

Photoautotrophic - energy from sunlight - photosynthesis

Cyanobacteria (old name - blue-green algae)

Chemoautotrophic - harvest energy from inorganic chemicals

Some involved in nitrogen fixation in where they live symbiotically in the root nodules of plants like peas

Metabolic Diversity

Heterotrophs - obtain at least some of their carbon from organic molecules like sugars or fats

Photoheterotrophs - use energy from the sun for photosynthesis - but their carbon comes from molecules produced by other organisms

Purple bacteria - live in sediments of ponds, mudflats and lakes

Chemoheterotrophs - obtain energy and carbon from organic molecules - decomposers and most pathogens

E. coli (some harmless some pathogenic) and Salmonella (food poisoning)

Size & Shape

Usually 0.2-10 mm

Some larger

Coccus, bacillus or spirillum

Structure of a Bacterium

DNA not bounded by membrane

Reactions commonly take place in the cytoplasm

A wall usually surrounds a plasma membrane

Walls usually peptidoglycan - peptides crosslink polysaccharides

Wall properties can be used to identify different species

Gram stain (positive or negative)

Structure of a Bacterium

A sticky mesh or slimy layer may surround the cell wall - helps them stick to surfaces

Some have flagella - structurally different from eukaryotic cell flagella

Some have pili - filamentous protein that stick out - help them adhere to surfaces & each other

The Archea

Methanogens - anaerobic - use electron transport system that ends with methane gas

Thrive in swamps, sewage, stockyards and the animal gut

Halophiles - live in brackish ponds, salt lakes & volcanic vents

Extreme Thermophile - inhabit such places as hot springs (Yellowstone Nat. Pk.) hydrothermal vents on the ocean floor or highly acidic soils

Bacteria

Include

Cyanobacteria (blue-green algae) - photoautotrophs

Chemoautotrophs - Rhizobium that fixes nitrogen in the root nodules of peas

Decomposers in soil - chemoheterotrophs

Enterobacteria

E. coli - enteric bacterium - gives us vitamin K (blood clotting)

Pathogens

Clostridium botulinum - can taint fermented grain & food improperly preserved (caned foods)

Characteristics of Viruses

A noncellular infectious agent

Consists of a protein coat surrounding a a nucleic acid core (genetic material)

A virus cannot reproduce itself - it can only be reproduced after it enters a host cell & takes over control of the cell

Viral Multiplication

Attachment

Must recognize specific molecular groups on the surface of the cell

Penetration

Either the whole viruses or its genetic material

Replication & synthesis

Viral genetic material directs the host cell to make copies of the viral nucleic acid and proteins including enzymes

Viral Multiplication

Assembly

New viral particles are formed

Release

New virus particles are released from the host cell

Viral Multiplication or Replication

Viral Multiplication or Replication

Viral Infection